By RICHARD ELLIS

n 1882, a former congressman from Minnesota named Ignatius Donnelly published a book titled ''Atlantis: The Antediluvian World,'' in which he argued that Plato's description of Atlantis was literally correct -- that it was indeed a large island at the mouth of the Mediterranean, the remnant of an Atlantic continent. Donnelly died in 1901, leaving no autobiography, so we will never know if he genuinely believed Plato's story was fact, or that the sunken continent of Atlantis connected America and Africa, but it seems reasonable to assume that he did.

Now comes ''The Farfarers,'' by Farley Mowat, a book not unlike Donnelly's in that it presents a revisionist view of history with little but the author's enthusiasm to support the thesis and, in Mowat's case, a desire to tweak the establishment view. (In his foreword, Mowat quotes Edward Gibbon as follows: ''I owe it to myself and to historic truth to declare that some circumstances . . . are founded only in conjecture and analogy.'') When not improvising history, Mowat relies here on the work of a kindred spirit, a maverick Canadian archaeologist named Thomas Lee. On the shore of Ungava Bay, Lee found evidence of what he believed might be ''the earliest European settlement in North America,'' but no other archaeologists supported his findings and he had trouble obtaining funding for future projects.

Mowat's saga goes like this: Several centuries before Norsemen like Leif Ericson arrived in North America, some other wayfarers (one must assume that the title of Mowat's book is to be pronounced ''far-fair-ers'') came to what is now the Canadian Arctic and Newfoundland in skin boats and settled there, building houses of stones. There were no trees with which to build roofs, so they used their overturned boats. ''Although walrus are today restricted almost exclusively to Arctic waters,'' Mowat writes, ''they were formerly found in Europe south to the Bay of Biscay and, in the western Atlantic, as far to the south as Cape Cod,'' and these people followed the herds and subsisted by selling valuable walrus ivory to Europeans. (The authority for the statement about the historical distribution of walrus is Mowat himself; he refers readers to his 1984 book, ''Sea of Slaughter,'' for verification.)

Mowat calls these early voyagers and capitalists ''Albans,'' and says that they were displaced by the fair-haired, pale-skinned Keltoi, who were ''ruled by a warrior caste'' and were ''slavers and sometimes headhunters.'' The Keltoi, of course, were the Celts, and they drove the Albans out of England, after which the dispossessed Albans began a migration across the North Atlantic, first arriving in Iceland (which Mowat says the Albans knew as Tilli), then moving to Greenland (Crona) and finally to Canada, where most of the boat-roofed houses have been found.

If you think wintering in the high Arctic in a stone house with a roof made from animal hides would be slightly uncomfortable, Mowat would like to disabuse you of that misconception. ''We southerners tend to envisage winter in the Arctic as a dread and miserable time of cold and famine,'' he writes. But for the early dwellers there, ''winter would normally have been a relaxed and enjoyable season largely spent visiting, feasting, singing, making tools and clothing, making love and sleeping as long as one chose. If people felt cramped in their small houses they could go out on the lake and fish through the ice.''

''The Farfarers'' is more than one book; it is history, natural history, fiction, archaeology and pseudohistory. Mowat has interlarded his historical disquisitions with italicized sections in which he fills the gaps in the known historical record with fictional vignettes that, he believes, ''come as close to the realities as one can reasonably expect.'' These vignettes, if removed from this book and collected into a single historical novel, would make for fascinating reading. Mowat writes engagingly and convincingly, but he provides no evidence whatever to back up his claims. Indeed, virtually all his conclusions are speculations. Few if any students of North American settlement agree with Mowat, and this would appear to be more than acceptable to him. He's a contentious fellow who was once denied entrance to this country because he claimed to have fired a rifle at United States Air Force jets flying overhead. He has frequently bemoaned the loss of Canada's indigenous wildlife, and ''Sea of Slaughter'' was an angry, articulate howl of protest.

In ''The Farfarers'' he again brings up the elimination of the great auk, a tall, flightless bird that was last seen alive in 1844. Here is his description of what he imagines the Albans' great-auk hunt would be like: ''They moved with shoulders hunched as if against the weight of life above them. Not 20 feet from the landwash they were met by serried ranks of great auks so closely packed as to stand almost shoulder to shoulder. This was an army of occupation a hundred thousand strong. The nearest auks faced the invaders with bodies erect and fearsome beaks thrust forward. The men moved warily, each holding a long, pointed paddle before him like a lance. The leader fingered his amulet once again and, in a voice inaudible above the cacophony, apologized for what was to follow.''

Because Mowat is such a marvelous writer, it almost doesn't matter if you accept his far-fetched tale of the Albans building stone houses with leather boats for roofs as they followed walrus herds across the North Atlantic. He certainly has not proved his case. But then again, nobody has been able to show that the ''Albans'' -- who might not even have existed -- didn't do what he imagines they did. It's impossible to prove a negative, and, like Donnelly's ''Atlantis'' (which went through 50-odd editions and is still in print), ''The Farfarers'' is worth reading, if for no other reason than to experience a provocative, alternative version of history, written by a master storyteller.

Richard Ellis is the author of ''Imagining Atlantis'' and ''The Search for the Giant Squid.''